当鼠标左键按下时,如何更改鼠标光标？

在Delphi 2007中,在鼠标移动事件中,我尝试使用以下命令更改鼠标光标:

procedure TFr_Board_Display.PaintBox_Proxy_BoardMouseMove(Sender: TObject;
  Shift: TShiftState; X, Y: Integer);
begin

  if left_mouse_button_down then begin  
    if some_condition then begin
      Cursor := crDrag;
    end
    else begin
      Cursor := crNoDrop;
    end;
  end
  else begin
    if some_other_condition then begin
      Cursor := crHandPoint;
    end
    else begin
      Cursor := crDefault;
    end;
  end;
end;

例如.但是,当鼠标左键按下时,我移动鼠标,光标不会更改为crDrag或crNoDrop.执行代码(例如Cursor:= crDrag;)但光标不会改变.当鼠标左键向上,我移动鼠标时,光标没有任何问题.

(我最初尝试使用一些Drag&Drop事件和属性,但无法按照我想要的方式工作.)

编辑:澄清所需的行为和格式化的代码.

编辑:谢谢你,Gamecat,但我希望当鼠标左键关闭时光标改变,鼠标移动光标时应该在crDrag和crNoDrop之间来回切换.

如果你在OnMouseDown中设置鼠标光标并在OnMouseUp中重置它,任何工作正常:

procedure TForm4.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  Cursor := crCross;
end;

procedure TForm4.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  Cursor := crDefault; // Or you can restore a saved cursor.
end;

如果希望鼠标移动时鼠标光标作出反应,请使用以下命令:

procedure TForm4.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  if ssLeft in Shift then begin
    if X<100 then
      Screen.Cursor := crCross
    else
      Screen.Cursor := crHourGlass;
  end else
    Screen.Cursor := crDefault;  // Or you can restore a saved cursor.
end;

procedure TForm4.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  Screen.Cursor := crDefault; // Or you can restore a saved cursor.
end;

需要MouseUp,否则如果光标悬停在控件上方,光标将不会变回.

一定要到处使用Screen.Cursor.

稍微偏离主题,但也许对你有用.

我创建了一个全局堆栈来允许嵌套的游标更改.它允许任何代码将鼠标光标设置为他们想要的内容,而不必担心他们的调用者或被调用者将其设置为什么.

例如:

procedure AskUserWhatToDo;
begin
  PushMouseCursor(crArrow);
  try
     if MessageDlg('Abort?', mtConfirmation, [mbYes, mbNo], 0) = mrYes then
        SysUtils.Abort;
  finally
     PopMouseCursor;
  end;
end;

procedure LongProcess;
begin
  PushMouseCursor(crHourglass);
  try
     //  do something
     if QuestionableState then
       AskUserWhatToDo;
     //  do something
  finally
    PopMouseCursor;
  end;
end;

两个程序都不必担心对方需要什么状态或离开鼠标光标.

//===============================================================
//   in a universal utility module (mine is called CraftWindows.pas)

function SetMouseCursor(ACursor : TCursor) : TCursor;
begin
   Result := Screen.Cursor;
   Screen.Cursor := ACursor;
end;

var
   GlobalMouseCursorStack : TList = nil;

procedure PushMouseCursor(ACursor : TCursor);
begin
   if GlobalMouseCursorStack = nil then
       GlobalMouseCursorStack := TList.Create;

   GlobalMouseCursorStack.Add(Pointer(SetMouseCursor(ACursor)));
end;

procedure PopMouseCursor;
begin
   if (GlobalMouseCursorStack <> nil) and (GlobalMouseCursorStack.Count > 0) then
   begin
       SetMouseCursor(TCursor(GlobalMouseCursorStack.Last));
       GlobalMouseCursorStack.Delete(GlobalMouseCursorStack.Count - 1);
   end;
end;

...

finalization
  GlobalMouseCursorStack.Free;